Hard to say, but you are using w3 total cache, with the minifier or without? And you also got Cloud Flare. I am just wondering if perhaps you got something stuck in your cache somewhere that’s old and during the time one cache is rebuilt it displays something incorrectly.

Also you are using some curious css z-index numbers… z-index:99990999999999 .. are you sure that number can be understood by your computer? looks a bit large to me unless you have 64 bits or more.

You also have invalid css in a number of places. in your media queries, you are not defining size correctly:

@media only screen and (min-device-width: 1701) and (max-device-width: 2000) {

1701 and 2000 px/em/pt?

the correct way to do it as you have in a different part of the custom.css file

@media screen and (max-width: 800px) {

}

also you have many other errors with your css (below, should be no space between 20 and px.

padding-top:20 px;

this is not a standard css defintion.

background-position-x:96%;background-position-y:90%;

I would suggest that you download a fresh flashlight theme, and replace your css with the one contained in there. You probably need an update as well since a few days ago a new version came out. Please do not compress css using software , unless you are just removing empty space, since almost everything out there screws up the css, since its supposed to go in a certain order, a cascade, and often optimizer move things around in a bad way.